The price relationship between cotton and polyester is being recalibrated by an energy shock. As Brent crude settled above $100 a barrel, its highest since late May, ICE's most-active December cotton contract rebounded from a three-week low of 85.56 cents/lb to close at 87.28 cents/lb, up 0.96 cent or 1.11%. For the textile supply chain, this is not merely a commodity price fluctuation but a signal that the fiber substitution logic is being forcibly rewritten by cost-side forces.
Cost Substitution: How Oil Props Up Cotton
PTA and MEG, the core raw materials for polyester, are directly linked to crude oil prices. When oil reaches triple digits, the full production cost of polyester staple fiber and filament yarn is systematically elevated, improving cotton's cost-performance ratio in spinning mills' blending formulas. Industry data shows the Cotlook A Index stood at 96.10 cents/lb that day, up 10 points from the previous session, indicating the spot market has begun tracking futures sentiment.
A softer dollar amplifies this effect. With the dollar index hovering near a two-week low, dollar-denominated commodities become cheaper for overseas buyers, potentially lifting purchasing interest from Turkey, Vietnam, Bangladesh and other major cotton importers. Yet it is important to recognize that cost substitution provides a floor, not a driver. Whether cotton prices can sustain a rebound ultimately depends on whether end demand is willing to absorb higher raw material costs.
Supply Side: Falling Ratings Versus Brazilian Abundance
Supply-side signals are clearly diverging. USDA's weekly crop progress report showed US cotton good-to-excellent ratings fell to 34% as of September 6, down from 39% the prior week and 54% a year earlier. The consecutive decline suggests downside risks to new-crop quality and yield. The harvest rate stood at 7%, matching last year and slightly above the five-year average of 6%, a pace that is hardly bullish on its own.
The real pressure comes from South America. Consultancy Agroconsult raised its 2025/26 Brazilian cotton output forecast by about 300,000 tonnes to a record 4.5 million tonnes. Brazil's continued expansion is reshaping global cotton trade flows. For Chinese buyers, Brazilian cotton's landed cost and supply reliability have made it a third force alongside Australian and US cotton that cannot be ignored. With ICE deliverable No. 2 cotton stocks unchanged at 54,414 bales, the market shows no obvious squeeze pressure.
The Event Anchor: Waiting Game Ahead of WASDE
The real pricing window comes this Friday. USDA's World Agricultural Supply and Demand Estimates report will be released, and traders will use it to assess US and global cotton supply-demand dynamics, evaluating how the approaching Northern Hemisphere harvest and recent price weakness may reshape the outlook. Before the report lands, the tug-of-war between support and resistance levels will likely persist.
Notably, the triggers for this rebound—oil and the dollar—are external variables outside cotton fundamentals. The Middle East tanker attacks have heightened energy supply concerns, but geopolitical premiums are highly uncertain. Once tensions ease, polyester cost support will quickly fade. For textile enterprises, building procurement decisions on short-term oil price swings creates excessive risk exposure.